Iron-deficiency anemia (IDA) in the absence of overt rectal bleeding often results from chronic occult blood loss or impaired iron absorption from the gastrointestinal tract (GIT). Many gastrointestinal conditions may predispose to IDA, including GIT cancers (most commonly colorectal cancer and gastric cancer), inflammatory bowel diseases (IBD), celiac disease, peptic ulcer disease (PUD), erosive esophagitis or gastritis, chronic atrophic gastritis and vascular ectasias, most of which carry long-term health risks in the absence of definitive treatment [1, 2, 3]. The vast majority of these disorders occur primarily in either the proximal (proximal to the ligament of Treitz) or the distal GIT (terminal ileum and/or colon) [1]. Therefore, in the absence of another apparent cause for IDA, it is standard to perform structural investigations of these areas, including colonoscopy (with intubation of the terminal ileum) and esophagogastroduodenoscopy (EGD), with the choice of initial investigation guided by the clinical history [4]. Historical studies have reported rates of clinically significant lesions (CSLs) found on EGD and colonoscopy of 40-70% during investigation of IDA [5, 6].
When EGD and colonoscopy fail to demonstrate CSLs that account for asymptomatic IDA, practitioners must consider whether to further investigate the deeper small bowel. This often requires tests that are not routinely accessible, invasive, resource intensive and/or expose patients to ionizing radiation, including deep balloon enteroscopy (DBE), video capsule endoscopy (VCE), computed tomographic enterography (CTE) and magnetic resonance enterography (MRE) [7, 8]. While historical studies have reported rates of CSLs in the small bowel in the context of IDA ranging from 32% to 78% [9] following negative EGD and colonoscopy, most of these studies included patients with overt and occult bleeding. The few studies that have specifically evaluated obscure occult IDA cite much lower rates of positive findings, with MR enterography being normal in 92.5% of subjects in one study [10]. Nevertheless, many practitioners may feel compelled to proceed with small bowel investigations, particularly in elderly individuals, for fear of missing small bowel cancers, Crohn’s disease or vascular ectasias that are at risk of re-bleeding. The reported prevalence of small bowel cancers in the general population, including adenocarcinoma, lymphoma, stromal tumours and others, is 1 to 1.5 per 100,000 persons [11, 12].
Societal guidelines provide variable recommendations regarding investigation of the small bowel in individuals with asymptomatic IDA. Most recommendations group these individuals together with those who have overt GIT bleeding. The American College of Gastroenterology (ACG) and European Society of Gastrointestinal Endoscopy (ESGE) recommend VCE in all patients with IDA following negative upper and lower endoscopy, with or without overt bleeding, whereas the Canadian Association of Gastroenterology (CAG) recommends small bowel imaging in select individuals [13, 14, 15]. VCE is universally recommended as the first-line test in this setting [13, 14, 15]. However, VCE is not readily available in many institutions and the cost is not always re-imbursed by third-party payers. Therefore, radiographic tests, such as CTE and MRE, are frequently substituted as first-line tests to evaluate the small bowel in this context. Notably, the yield of CTE and MRE are reported to be considerably inferior to VCE for diagnosing small bowel lesions, albeit not all lesions identified on VCE might be considered clinically significant in these studies [16, 17, 18].
Overall, there remains considerable uncertainty regarding the appropriate investigation of asymptomatic IDA, and particularly the value of small bowel imaging, in persons with who have a negative EGD and colonoscopy. As IDA occurs in up to 12% of people in industrialized countries and 45% in non-industrialized countries, gastrointestinal investigations in these patients potentially represent a significant source of health care resource utilization [19]. Therefore, we assessed the frequency and nature of CSLs (i.e. those potentially requiring therapy) observed during EGD, colonoscopy and small bowel imaging studies in the investigation of persons aged 50 years or older with IDA in the absence of overt bleeding at our referral center.
DATA SOURCES
We identified persons aged 50 years or older who underwent colonoscopy at The Ottawa Hospital using the Ottawa Hospital Data Warehouse, a repository of clinical, laboratory, imaging and pathological information for all patient encounters at The Ottawa Hospital. We conducted a detailed chart review in all patients to identify those who had received a complete colonoscopy (i.e. intubation of cecum or terminal ileum) with a reported adequate bowel preparation, as well as to identify procedural indications and CSLs on endoscopy, based on endoscopy and pathology reports.